Technical Abstract:
Tomatoes have been implicated in fourteen outbreaks of salmonellosis in the U.S. since 1996. Previous research in our laboratory has documented the inadequacy of washing processes to inactivate and/or remove microorganisms on tomatoes, including human pathogens, due to biofilm formation and inaccessibility of microbial attachment sites to washing systems.
The objective was to develop chlorine dioxide gas (ClO2) treatment capable of inactivating human pathogens attached to inaccessible sites within biofilm on the tomato surfaces.
Tomatoes were inoculated with Salmonella Poona RM 2350 to an approximate final concentration of 5 log CFU/gm, and stored at 4C for 24 h prior to treatment. Tomatoes were fumigated with ClO2 for up to 6 h in a closed chamber that was developed at ERRC, using two different technologies for generating ClO2. Following treatment, residual populations of Salmonella Poona on whole cantaloupe rinds were enumerated using XLT-4 selective agar medium.
There was in excess of 4.5 log CFU/gm reduction in Salmonella Poona populations following ClO2 treatment for 6 h. Population reductions following ClO2 treatment were similar irrespective of the technology used to generate ClO2. The treatment helped increase the shelf life of the tomatoes by reducing the spoilage microorganism populations on the surface, and did not seem to have adverse effects on the quality of this commodity.
The work presented here showed that ClO2 treatment of tomatoes is able to inactivate Salmonella Poona attached to inaccessible sites such as the stem scar area. Also, this treatment was shown to extend the shelf life at 4C and had no adverse effects on the quality of the tomatoes.